采用粒子成像测速技术(PIV)研究结冰翼型表面气泡分离
The separation bubble on a NACA 0012 airfoil with a two-dimensional, constant span,simulated leading-edge glaze-ice accretion is investigated using Particle Image Velocimetry(PIV). Chordwise PIV measurements, or those along the separation bubble cross-section,are obtained at a Reynolds number of 0.9x106, Mach number of 0.20, and between 0 degand 5 deg angle-of-attack. Mean reattachment estimated from surface oil-flow visualizationindicates increasing bubble length and unsteadiness (based on reattachment zone width)with angle-of-attack, consistent with results extracted from PIV measurements. Timeaveragedstreamlines and forward flow intermittency reveal a primary recirculation withclockwise rotation defined by a shear layer and a smaller, secondary recirculation withcounter-clockwise rotation directly downstream of the point of separation, both consistentwith backward-facing step type flowfields. Mean and RMS velocity component contourshighlight these features and wall-normal profiles are extracted and compared to otherseparation bubble data including those over a backward-facing step and blunt flat plate.